Electromagnetic fuel pumps are subject to demands that are not made on other types of pumps. In view of their intended use in association with motor vehicle, marine, generator, military, and agricultural applications, electromagnetic pumps must be capable of maintaining long-term, stable operational lives under extremely adverse working conditions. In addition, since millions of applications require fuel pumps, the number of electromagnetic pumps that are produced on an annual basis is high. Hence, cost considerations relating to pump manufacture dictates that a minimal number of parts be utilized. In addition, manufacturing processes must be accurate and reproducible such that identical pumps are produced. Finally, the manufacture of electromagnetic fuel pumps must be simple such that pumps can be quickly assembled using ordinarily skilled labor.
Both internal and external variables impact a pump's performance. Fuel, which in most instances comprises gasoline, or diesel, are aggressive solvents that are capable of deteriorating internal components of a pump. As a result, pump components must be protected from contact with the solvents. Various configurations of O-rings and sealing collars have been disclosed in the prior art for preventing such contact.
External factors, such as temperature, humidity, and fluid leaks, can also contribute to the problematic effects of pump instability and lead to shorter pump lifespan. Such factors can cause excitation timing circuits to behave irregularly, or they can accelerate the deterioration of the mechanical and electrical components of the pump. The incursion of salt water into pumps during the winter months in northern climates can also cause extensive damage to both the mechanical and electrical components of a pump. Such damage is usually attributed to the accelerated corrosion effects of the galvanic circuit created by salt water and dissimilar metals present within electronic circuits.
The formation of pump housings has typically been one of the most difficult stages in the construction of an electromagnetic fuel pump. Known methods have generally included the bending of U-shaped yokes, assembly of multiple stamped sheet metal pieces, or foam filling completed assemblies for environmental compatibility. Unfortunately, these types of designs have been problematic in assembly and have been particularly unreliable in use. In known pump designs, such as that shown in FIG. 1, inlet and outlet ports have conventionally been components that are separate from the pump housing with which they communicate. Inlet and outlet ports have been traditionally detachably secured to housings by means of threaded nuts and the like. Assembly of the pump inlet and outlet ports has heretofore been very labor-intensive.
Additionally, the location tolerances of moving parts of a pump have also presented challenges to the construction of electromagnetic pumps. Alignment of moving components, with respect to the inlet and outlet ports of a pump, requires highly accurate methods of assembly. Previous methods have utilized the pump housing to locate the surfaces to which the pump is built and aligned. Constraints created by the bending of U-shaped yokes and the stamping of individual metal housing pieces has limited the manufacturer's ability to coaxially align the inlet port, the outlet port, and the moving pump components. Such lack of coaxial alignment can reduce the pump efficiency and the stability of the pump performance.
Furthermore, pumps known in the art typically comprise driving circuits that include a dual winding coil, i.e., one magnetic winding and one oscillator feedback winding. The coil together, with resistors, diodes, a transistor, and a power source, comprise the oscillator circuit, which drives the pumping mechanism. The dual winding coil requirement of most current pumps presents problems related to pump manufacture. For example, in order to manufacture a pump comprising two differently gauged coil wires, the manufacturer must stock and store the two differently gauged coil wires, which can be costly in terms of materials and space requirements. In addition, one winding is of a very small and fragile gauge wire.
Known pumps have also suffered from the lack of on-board EM hardening and surge suppression circuitry.
Thus, there has been a longfelt need for an electromagnetic fuel pump with inlet and outlet ports that are integral to the pump housing and have on-board surge suppression and EM hardening.